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Low-Resolution Spectroscopy of the Recurrent Nova T Pyxidis at its Early Stage of 2011 Outburst

We present our observational results of the recurrent nova T Pyxidis at its early stage of 2011 outburst, using a low-resolution spectrograph ($R\approx400$) attached to a 28cm telescope. Total nights of our observation are 11, among which 9 nights are during the pre-maximum stage. As a result we have obtained a detailed evolutional feature of this recurrent nova on the way to its maximum light. At first, on the earliest three nights ($-25 \sim -21$ days before maximum), broad and prominent emission lines such as Balmer series, He I, He II, N II, N III and O I together with P Cygni profile are seen on the spectra. The blueshifted absorption minima of H$α$ yields a maximum expansion velocity of approximately 2200 km s$^{-1}$, and the velocity gradually decreases. Then, Helium and Nitrogen lines are weakened day by day. After that (18 days before maximum light), Fe II (multiplets) lines emerge on the spectra. These lines are then strengthened day by day, and the P Cygni profiles also become more prominent. Accordingly, the expansion velocities turns to be gradual increase. In addition, during the pre-maximum stage, nova spectral type of T Pyx is thought to evolve from He/N type to Fe II one.